The present invention relates to fuel injectors for injecting liquid fuel into internal combustion engines or fuel reformers; more particularly, to such fuel injectors having heat exchanging means whereby coolant may be circulated through the exchanging means to cool the fuel injector; and most particularly, to a fuel injector having an integral heat-exchanging jacket connected to the inlet port of the fuel injector for cooling the fuel injector and heating the incoming fuel. The invention is especially useful in preheating fuel being supplied to high-temperature fuel cell reformers.
Fuel injectors are well known for supplying metered amounts of fuel to combustors, such as internal combustion engine cylinders, and reformers, such as hydrogen/reformate generators for fuel cells.
Two problems with such use are also well known in the art. First, fuel injectors are required to operate in a relatively high-temperature environment, wherein the output force and working life of a solenoid actuator may be significantly reduced for known reasons. The solenoid is vulnerable to heat transmitted and radiated from the combustor or reformer, as well as to its own resistance-generated heat. Second, fuel supplied to the combustor or reformer is preferably vaporized before being reacted. In engines, an increase in fuel temperature typically is provided by adiabatic compression of the charge. In reformers, no comparable mechanical heat source is available.
U.S. Pat. No. 4,351,480, issued Sep. 28, 1982 to Masaki et al., discloses a specially-configured fuel injector for an internal combustion engine wherein the fuel path within the injector includes an inlet, a manifold portion including the metering apparatus of the injector, and an outlet. Fuel is circulated continuously through the injector to both cool the injector and heat the fuel. A disadvantage of this invention is that only a portion of the heated fuel is used immediately and a return path to a fuel storage tank or other reservoir means for the fuel is required. A further disadvantage is that the invention requires a complete redesign of the fuel injector and cannot be used with a prior art fuel injector.
U.S. Pat. No. 5,915,626, issued Jun. 29, 1999 to Awarzamani et al., discloses a fuel injector for an internal combustion engine wherein the solenoid coil is wound on a thin-wall sleeve thermally coupled to the fuel path through the injector, whereby resistance heat is abstracted from the solenoid by the passage of fuel through the injector. The effectiveness of this invention is limited by the relatively small heat-exchanging surface of the sleeve. Further, this invention does not address directly the significant problem of solenoid heating from contact of the injector with the combustor or reformer. For fuel injectors used with high-temperature reformers, this is the predominant source of heat.
What is needed is a fuel injector heat exchanger means wherein a heat exchanger having a relatively large exchanging surface is disposed directly between the primary heating source (the combustor or reformer) and the fuel injector, and in the fuel flow path between a fuel source and the fuel inlet to the fuel injector.
It is a principal object of the invention to provide a fuel injector assembly wherein the operating temperature of the fuel injector is decreased and the temperature of the injected fuel is increased.
It is a further object of the invention to provide an improved fuel injector assembly having jacket means disposed between the injector means of the fuel injector and the principal source of heat being conducted and radiated into the fuel injector, whereby the fuel cell is thermally insulated from such principal source of heat.
It is a still further object of the invention to provide an improved fuel injector assembly whereby injected fuel is more easily vaporized.
It is a still further object of the invention to provide an improved fuel injector assembly wherein the solenoid operates at a lower temperature.
It is a still further object of the invention to provide an improved fuel injector assembly wherein a conventional prior art fuel injector may be incorporated without significant modification.
Briefly described, the present invention is directed to a fuel injector assembly incorporating a heat-exchanger jacket, the jacket and fuel injector being disposed for use in, for example, a bore in the head of an internal combustion engine or a bore in the vaporizer of a fuel reformer. The exchanger includes an inlet port; a heat exchanging means disposable in the bore in direct contact with the head or vaporizer; the dispensing portion of the fuel injector; and an outlet port connected to the inlet port of the fuel injector, such that fuel entering the fuel injector is preheated by passage through the exchanger. In some applications, it may be desirable to maintain the fuel at a high pressure to prevent premature vaporization of the fuel in the jacket and resulting vapor lock of the fuel system.